diff --git a/lemon/bits/lp_id.h b/lemon/bits/lp_id.h
new file mode 100644
--- /dev/null
+++ b/lemon/bits/lp_id.h
@@ -0,0 +1,157 @@
+/* -*- mode: C++; indent-tabs-mode: nil; -*-
+ *
+ * This file is a part of LEMON, a generic C++ optimization library.
+ *
+ * Copyright (C) 2003-2008
+ * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
+ * (Egervary Research Group on Combinatorial Optimization, EGRES).
+ *
+ * Permission to use, modify and distribute this software is granted
+ * provided that this copyright notice appears in all copies. For
+ * precise terms see the accompanying LICENSE file.
+ *
+ * This software is provided "AS IS" with no warranty of any kind,
+ * express or implied, and with no claim as to its suitability for any
+ * purpose.
+ *
+ */
+
+#ifndef LEMON_BITS_LP_SOLVER_ID_H
+#define LEMON_BITS_LP_SOLVER_ID_H
+
+namespace lemon {
+
+  namespace _lp_bits {
+
+    struct LpIdImpl {
+      std::vector<int> index;
+      std::vector<int> cross;
+      int first_index;
+      int first_free;
+    };
+
+    class LpId {
+    public:
+
+      class IdHandler {
+      public:
+        virtual ~IdHandler() {}
+        virtual int addId(LpIdImpl&) = 0;
+        virtual void eraseId(LpIdImpl&, int xn) = 0;
+      };
+
+      LpId(int min_index = 0) {
+        id_handler = 0;
+        impl.first_free = -1;
+        impl.first_index = min_index;
+        impl.cross.resize(impl.first_index);
+      }
+
+      LpId(const LpId& li) {
+        id_handler = 0;
+        impl = li.impl;
+      }
+
+      LpId& operator=(const LpId& li) {
+        id_handler = 0;
+        impl = li.impl;
+        return *this;
+      }
+
+      void setIdHandler(IdHandler& ih) {
+        id_handler = &ih;
+      }
+
+      int fixId(int fn) const {return impl.cross[fn];}
+      int floatingId(int xn) const {return impl.index[xn];}
+
+      int addId() {
+        if (id_handler == 0) {
+          int xn, fn = impl.cross.size();
+          if (impl.first_free == -1) {
+            xn = impl.index.size();
+            impl.index.push_back(fn);
+          } else {
+            xn = impl.first_free;
+            impl.first_free = impl.index[impl.first_free];
+            impl.index[xn] = fn;
+          }
+          impl.cross.push_back(xn);
+          return xn;
+        } else {
+          return id_handler->addId(impl);
+        }
+      }
+
+      void eraseId(int xn) {
+        if (id_handler == 0) {
+          int fn = impl.index[xn];
+          impl.index[xn] = impl.first_free;
+          impl.first_free = xn;
+          for(int i = fn + 1; i < int(impl.cross.size()); ++i) {
+            impl.cross[i - 1] = impl.cross[i];
+            impl.index[impl.cross[i]]--;
+          }
+          impl.cross.pop_back();
+        } else {
+          id_handler->eraseId(impl, xn);
+        }
+      }
+
+      void firstFloating(int& fn) const {
+        fn = impl.first_index;
+        if (fn == int(impl.cross.size())) fn = -1;
+      }
+
+      void nextFloating(int& fn) const {
+        ++fn;
+        if (fn == int(impl.cross.size())) fn = -1;
+      }
+
+      void firstFix(int& xn) const {
+        int fn;
+        firstFloating(fn);
+        xn = fn != -1 ? fixId(fn) : -1;
+      }
+
+      void nextFix(int& xn) const {
+        int fn = floatingId(xn);
+        nextFloating(fn);
+        xn = fn != -1 ? fixId(fn) : -1;
+      }
+
+    protected:
+      LpIdImpl impl;
+      IdHandler *id_handler;
+    };
+
+    class RelocateIdHandler : public LpId::IdHandler {
+    public:
+
+      virtual int addId(LpIdImpl& impl) {
+        int xn, fn = impl.cross.size();
+        if (impl.first_free == -1) {
+          xn = impl.index.size();
+          impl.index.push_back(fn);
+        } else {
+          xn = impl.first_free;
+          impl.first_free = impl.index[impl.first_free];
+          impl.index[xn] = fn;
+        }
+        impl.cross.push_back(xn);
+        return xn;
+      }
+
+      virtual void eraseId(LpIdImpl& impl, int xn) {
+        int fn = impl.index[xn];
+        impl.index[xn] = impl.first_free;
+        impl.first_free = xn;
+        impl.cross[fn] = impl.cross.back();
+        impl.index[impl.cross.back()] = fn;
+        impl.cross.pop_back();
+      }
+    };
+  }
+}
+
+#endif